You know, the way people who knew you dead parents will try to make you feel better by talking what little they know about them?
I disagree. And Alfred already acknowledges Damian as Bruce's son.
Dick isn't 'someone who knew Dami's dead father'. Dick's not a family friend.
And Damian already refers to himself that way. IMO, that line's for us, not for Damian, to hear. And that Dick's acknowledging himself to be less of a son than Damian, because Dick is only adopted and raised by Bruce, not an inheritor of Bruce's blood.